NORTHERN NATURAL GAS CO — Gas transmission and gathering — incident on 2017-01-11

Gas transmission and gathering incident in Not Within a Municipality, OTTAWA County, KS. Reported cause: EQUIPMENT FAILURE. Reported consequences: 0 fatalities, 0 injuries, 4900 NATURAL GAS released, $200 reported property damage. Operator-reported incident data submitted to PHMSA, generally within 30 days. Records may be supplemented or corrected and do not represent final agency causal findings.

Report number: 20170024.

Operator ID: 13750.

Reported incident date: 1/11/2017 19:45.

Location detail: 0

Cause detail: MALFUNCTION OF CONTROL/RELIEF EQUIPMENT

Cause detail: ON JANUARY 11, 2017, AT 1945 HOURS, THE OPERATIONS COMMUNICATION CENTER RECEIVED A CALL FROM A TENANT NEAR THE TESCOTT COMPRESSOR STATION STATING THERE WAS A LOUD NOISE NEAR THE STATION. A NORTHERN NATURAL GAS TECHNICIAN ARRIVED AT THE STATION AT APPROXIMATELY 2030 HOURS AND DID NOT NOTICE ANY ABNORMAL CONDITIONS. UNIT 5 WAS ON LINE ON THE E MAINLINE WITH A MAOP OF 991 PSIG. HE FOUND THE RELIEF VALVE RAIN CAP WAS OFF. WHEN THE TECHNICIAN CHECKED THE PRESSURE TRENDS, HE FOUND THAT THE DISCHARGE RELIEF VALVE APPEARED TO HAVE OPENED AND CLOSED SEVERAL TIMES AT PRESSURES BELOW THE MAOP RANGING FROM 862 PSIG TO 921 PSIG. THE RELIEF VALVE IS INTENDED TO RELIEVE PRESSURE AT 1030 PSIG. GAS CONTROL DID NOT NEED THE UNIT AND IT WAS SHUT DOWN. ON JANUARY 12, 2017, TECHNICIANS BENCH TESTED THE RELIEF VALVE PILOT. A NEW SOFT GOODS KIT WAS INSTALLED IN THE PILOT AND THE PRESSURE WAS SET AT 1,030-PSIG. THE PILOT WAS INSTALLED ON THE RELIEF VALVE AND THE RELIEF VALVE LIFTED OFF THE SEAT AT 1030-PSIG WHEN TESTED. UNIT 5 WAS PLACED ON LINE AT 1127 HOURS. ON JANUARY 13, 2017, THE FACILITY PLANNING DEPARTMENT WAS CONTACTED TO CALCULATE THE GAS LOSS. FIELD OPERATIONS INDICATED THAT IT DID NOT SEEM THAT THE RELIEF VALVE WAS FULL OPEN DURING VENTING. THE RELIEF INCIDENT OCCURRED BETWEEN 19:10 AND 20:06. FLOW THROUGH THE LINE WAS CONSTANT DURING THE PERIOD AS MEASURED BY THE FLOW METER AT THE CLIFTON COMPRESSOR STATION 47.5 MILES DOWNSTREAM. THE INITIAL ESTIMATE INDICATED A GAS LOSS OF 6 MMCF. FACILITY PLANNING NOTIFIED FIELD OPERATIONS AND AN URGENT OPERATIONS COMMUNICATION CENTER CALL WAS INITIATED WITH THE PIPELINE SAFETY AND ENVIRONMENTAL DEPARTMENTS. THE NATIONAL RESPONSE CENTER WAS NOTIFIED IMMEDIATELY AFTER THE URGENT OPERATIONS COMMUNICATION CENTER CALL OF THE INCIDENT DUE TO THE GAS LOSS IN EXCESS OF 3 MMCF. ON JANUARY 17, 2017, A THOROUGH GAS LOSS ANALYSIS WAS COMPLETED BY FACILITY PLANNING. LIMITED WORK OCCURRED ON JANUARY 16, 2017, DUE TO THE ICE STORM. THE ESTIMATED GAS LOSS FROM THE INCIDENT IS 4.9 MMCF.

PHMSA trend classification: not significant, not serious.

PHMSA standardized cause: EQUIPMENT FAILURE — MALFUNCTION OF CONTROL/RELIEF EQUIPMENT.

PHMSA indexed costs: $17,400 reported total cost, $15,968.792 in 1984 dollars, $20,331.585 in current-year dollars.

PHMSA trend flags, standardized causes, and indexed costs are analytical fields added to operator-reported incident data. They do not represent final agency causal findings.